A transport network (TN) is used to carry data signals between a Radio Base Station (RBS), such as a NodeB or an eNodeB in 3G Long-Term Evolution (LTE) networks, and a Serving gateway (S-GW) or Packet Data Network gateway (PDN-GW). A TN may be operated by a mobile network operator or by a third party transport provider. In the latter case there would be a Service Level Agreement, SLA, between the mobile and transport operators. With the rapid growth of digital data telecommunications following the introduction of 3G and 4G technology, TNs may frequently act as bottlenecks in the overall data transport process. Thus, various systems and methods have been proposed for improving or prioritising the way that data packets are transported by the bearers.
Service differentiation in the Radio Access Network (RAN) is one supplementary means for more efficiently handling high volumes of traffic. As a simple example, using service differentiation a higher bandwidth share can be provided for a premium service, and in this way the overall system performance can be improved. As another example, a heavy service such as p2p traffic, can be down-prioritized. Implementing such service differentiation methods requires integration into the Quality of Service (QoS) concept of LTE and Universal Mobile Telecommunications System (UMTS) technology. Details of the QoS concept for LTE can be found in the 3rd Generation Project Partnership (3GPP) Technical Specification TS 23.410. The main idea of this concept is that services with different requirements use different bearers. When a User Equipment (UE) attaches to the network a default-bearer is established (typically a best-effort service). However, if the UE invokes services having different QoS parameters then a dedicated bearer is established for each service.
There is no common solution to provide efficient Radio Bearer (RB) level service differentiation over a Transport Network bottleneck. In International patent application No. PCT/EP2011/068023, the present inventors have described a mechanism for a per-bearer level service differentiation, that makes the bandwidth sharing among RBs more RAN-controlled. This is described further below in relation to FIG. 1. The mechanism employs the concept of “colour” profiling similar to that defined by the Metro Ethernet Forum (MEF) in MEF 23, Carrier Ethernet Class of Service—Phase 1 (See also http://metroethernetforum.org/PDF_Documents/Bandwidth-Profiles-for-Ethernet-Services.pdf.). As a way of indicating which service frames (or data packets) are deemed to be within or outside of the Service Level Agreement (SLA) contract colours are assigned to the data packets according to the bandwidth profile. Note that there is no technical significance to the colour itself, which is just used as a convenient way of describing and/or labeling the data packets. Levels of compliance are green when fully compliant, yellow when sufficient compliance for transmission but without performance objectives and red or discarded when not compliant with either. The data packets of a bearer are checked against the compliance requirements by a bandwidth profiler, for example a two-rate, three-color marker. This validation process can be used between two parties (e.g. between two operators) and can be the part of the SLA. In general, in the SLA different requirements are set for green packets and yellow packets. The green packets are “more important” than the yellow packets. To reflect this difference between two types of packets, at a bottleneck point such as on entry to a TN, a colour aware active queue management discards yellow packets in preference to green packets when there is congestion (i.e. insufficient bandwidth available in the TN to transport all data packets). Thus, for each RB a predefined profiling rate (i.e. green rate) is assigned based on the Quality QoS Class Identifier (QCI) of the RB. This mechanism allows bandwidth guarantees to be provided for the RBs, at least to a certain degree.
Referring to FIG. 1, this shows a schematic illustration of a TN employing bandwidth profiling for each of two bearers. The example is shown of an LTE system with two bearers 102, 104 each carrying data packets between a PDN-GW 106 and an eNodeB 108 via a S-GW 110 and through a TN 112. The Bearers 102, 104 are designated S5/S8 bearers 102a, 104a between the PDN-GW 106 and the S-GW 110, S1 bearers 102b, 104b from the S-GW 110 over the TN 112, and radio bearers 102c, 104c beyond the eNodeB 108. Each Bearer is assigned a bandwidth profiler—profiler 114 for bearer 102 and profiler 116 for bearer 104. Each of the bearers has an assigned QCI and an associated predefined ‘green’ rate (CIR) and bucket size. This example is of a single rate, two-colour profiler, in which data packets that are conformant with the green rate are designated as green packets, and packets that are not conformant are designated as yellow. It will be appreciated that the principles applied to the two-colour profilers described herein could readily be extended to three or more colours, in which case an additional rate would be specified (referred to as an Extended Information Rate—EIR) for each additional colour used.
Packets of each Bearer 102, 104 that conform with the bearer's profiler 114, 116 are marked as conformant packets 118 (i.e. assigned ‘green’) and packets that do not conform are marked as non-conformant packets 120 (i.e. assigned ‘yellow’). Because there are no ‘yellow’ rates assigned, all data packets that are not coloured ‘green’ by the profilers 114, 116 are assigned ‘yellow’. For example, assume that the ‘green rate’ is 5 Mbps for a Bearer and the bitrate of this Bearer is about 7.5 Mbps. In this case, approximately ⅓ of the packets of the Bearer will be assigned to ‘yellow’.
The TN 112 bottleneck active queue management can then use the colour information marked in the data packets when choosing which packets to drop when there is insufficient bandwidth (congestion). The first packets to be dropped will be the ‘yellow’ packets 120.
In the example described, a two-colour (green-yellow) profiler is used for each Bearer. The bucket size and ‘green’ rate at which rate the green tokens arrive into the buckets for each of the Bearers are set by the operator. When the profiler 114, 116 assigns a Packet either ‘green’ or ‘yellow’, this means that the packet is marked with the conformance information in such a way it can be used at the TN bottleneck buffer(s). For example the Drop Eligibility (DEI) bit of the packet's Ethernet frame, or the Differentiated Services Control Point (DSCP) field in the IP header could be used to indicate if a packet has been assigned ‘green’ or ‘yellow’.
Originally the colouring concept is used to specify service between two networks/operators. For example in the Service Level Agreement between the two operators they specify the Committed Information Rate (CIR or green rate) and the Excess Information Rate (EIR rate that is the maximum acceptable rate). Roughly speaking the service for green packets are guaranteed and service for yellow packets are only “best-effort” type. This means that the drop of yellow packets does not violate the SLA.
This colouring concept can also be used for improving per-service or per-bearer fairness at a bottleneck, as described in PCT/EP2011/068023. The colouring concept is used in a different way for a different purpose and at a different location (i.e. it is done in the RAN node instead of in the Mobile Back Haul, MBH, node). A green rate is assigned for a bearer (i.e. for a service of a user and roughly speaking a desired bitrate for that service) and data packets of the bearer that do not exceed this bitrate are coloured green, whereas data packets above the green rate are coloured yellow. In this case when a bearer has yellow packets that means that it has a higher bandwidth than the desired value (but gains from this higher bandwidth when the data packets are transported through the bottleneck), so the drop of these yellow packets probably does not have a serious negative impact on the service performance. Consequently, in this case the use of green and yellow packets improves the fairness of resource sharing among user services. Note that when the colouring concept is used for improving per-bearer fairness, then the colouring (i.e. profiling) is done in the RAN node where per-bearer handling is available.
In the above example, a static green rate configuration is used such that the profiler for each bearer uses a predefined green rate. The mechanism is implemented in a RAN node (e.g. Radio Network Controller, RNC, or Serving gateway, S-GW) and operates on a per-bearer basis. For example, if we would like to provide 1 Mbps bandwidth for a specific bearer, then we use a profiler for that bearer with 1 Mbps green rate. A packet of the bearer will be coloured according to this, such that when the bearer bitrate is below 1 Mbps all packets of the bearer will be coloured to green. When the bitrate is over 1 Mbps some packets will be coloured to yellow. At the transport network (TN) an Active Queue manager (AQM) uses colour aware dropping such that when there is insufficient capacity in the TN a yellow packet will be dropped first. This means that bearers that have yellow packets (i.e. their bitrate is above 1 Mbps) will suffer packet drops when there is congestion in the TN.
This static green rate setting can be used for a bearer (i.e. service) where the bandwidth requirement is known in advance—for example a streaming service. However, a relative service differentiation can be useful. For example to differentiate between a premium and a normal Internet access, then a premium user may get, say, 4 times more bandwidth than a normal user. In a High-Speed Downlink Packet Access (HSDPA) network this type of service differentiation is referred to as a Relative Bitrate (RBR) feature. As an option the static green rate setting can be used to approximate relative service differentiation. The static profiling rates for the bearers can be determined based on the typical TN link capacity and the typical traffic mix. When more colours are used, more link capacity and/or traffic mixes can be supported (e.g. with 3 colours 2 traffic mixes can be handled). However, the use of static green rates cannot provide relative service differentiation in all situations. In particular, a static profiling rate mechanism can only handle bottleneck capacity changes in per-bearer resource sharing to a limited extent by using more colours. Also, a static profiling rate mechanism cannot handle all traffic mixes in per-bearer resource sharing. This means that the existing mechanisms do not provide very efficient relative service differentiation.